Not applicable.
This invention relates to a multi-layer printable film, a molded article therewith, and to a process of preparing the molded article by Insert Mold Decoration (IMD).
Vinyl fluoride (PVF) and vinylidene fluoride (PVdF) are thermoplastic polymers which exhibit a combination of advantageous properties and in particular, a high chemical inertness and an excellent resistance to ultraviolet rays.
Polycarbonate (PC) films generally have acceptable levels of clarity, and strength, but lack acceptable levels of birefringence, chemical and UV radiation resistance for exterior automotive applications. For example, PC films generally have high birefringence, which is, in part, due to the levels of stress which are placed on the film during its formation. This stress is frozen into the film upon cooling.
It is generally known in theory to produce PC films by extruding heated resin and passing the extruded resin through the nip formed between two polished metal rolls. This process is typically unsuitable for producing low birefringence films because it introduces a high level of stress in the films which increases the birefringence of said films. A low birefringence film is required for 3-dimensional thermoformed (vacuum or pressure forming) articles prepared by IMD for applications that require tight graphics registration. Low birefringence provides part to part dimensional consistency and printing registration wherein the decorated film is formed using heat.
In U.S. Pat. Nos. 4,659,625 and 5,096,782 issued to Solvay and Cie, a laminated structure, which comprises a layer of PVdF bonded to a layer of PC using a vinyl acetate polymer, is assembled by heat lamination or coextrusion. This prior art suffers from the lack of low birefringence in the laminated structure.
In U.S. Pat. No. 5,304,413 issued to DuPont, a laminated structure which comprises a layer of PVF bonded to a layer of PC using an acrylic polymer, is assembled by heat lamination. This prior art also suffers from lack of low birefringence in the laminated structure.
The present invention is directed to multi-layer printable thermoplastic polymer films and articles and methods for making such films and articles. More particularly the article of this invention comprises a base layer of an injection molded, blow molded or extruded thermoplastic polymer and an overlay of a multi-layer printable film to form the multi-layer article. The multi-layer printable film preferably comprises a fluoride polymer layer laminated to a polycarbonate layer. Lamination can be through heat lamination or adhesive lamination.
The multi-layer printable film comprises an outer fluoride polymer layer to which is laminated a polycarbonate layer. The multi-layer printable film must have low birefringence and a low surface roughness, namely a smooth surface.
A method for producing the multi-layered printable film of this invention with properties of formability, low birefringence, chemical and UV radiation resistance and optical transparency is set forth herein. These laminated films are well suited for exterior automotive applications prepared by the IMD process. IMD is the process by which the pre-formed multi-layer printable film is placed in a mold and a thermoplastic polymer melt, which forms the base layer, is molded to the exposed side of the printable film which exposed side becomes the interface between the decorative multi layer overlay film and the base layer. The base layer to which the decorative overlay film is laminated can be any suitable thermoplastic resin. Suitable thermoplastic resins for use in this invention for the base layer are available from the GE Plastics component of General Electric Company under the trademarks: Lexan(copyright) (an aromatic polycarbonate), Cycolac(copyright) (an acrylonitrile-butadiene-styrene polymer [ABS]), Cycoloy(copyright) (an aromatic polycarbonate/ ABS polymer composition), Noryl(copyright) (a modified polyphenylene ether resin composition), Valox(copyright) (polybutylene terephthalate) resin, Ultem(copyright) (polyetherimide) resin, homopolycarbonates, copolycarbonates, copolyestercarbonates, and mixtures thereof with other polymers.